Hi all, I promised to keep everybody posted on the main air jet issue.

Just to recap, my 650, and a lot of others around here are running really great at all RPM's and throttle positions except, except full throttle top speed. I am sure I have the needle and jets right.

However, I felt that the main air jet is too big after airbox mods, dynojet, and exhaust mods so I went looking for different main air jets.

Keihin US told me they can't look up the jet series for our carbs.
Sudco - No response.
Dealer - Duh? (way over their heads)

Anyway I bought one and took a picture of it. My camera can't take good photos of stuff this small. It is barrel shaped with no threads. It is .12" long, .08" wide (yeah, it is just a speck).

Anybody have any experience with jets this small?
Hard to change?
Possible to change?

I will let you know what Keihin tells me.

 

I have rebuilt a carb that some kid took apart & could not get back together. When I got it back together, I had a jet like that left. Bike ran great & is still runnung great, but it must be missing a part. OOOPS!

 

pardon my stupidity, but i`m in the middle of the dynojet kit install
and i do not know where the main jets are located...

if it said "holley on it no problem..

 

It is the big copper colored thing with a flat head slot in it on the bottom of the carb under the bowl!

 

thanks 2fat! i already found it and have problems getting it to run....

 

Nyroc try this,134f-138r 4th notchand 3 turns on the air screw. These things are lean out of the box.I have simlar mods as you and can run 67 to 69 mph consistantly.I ride at 1000 to 1500 ft near tug hill.[img]i/expressions/face-icon-small-cool.gif[/img]

 

Hey Nyroc even though dyno jet makes a fine product try the kawi jet with stock jet that was in the rear put it to the front and a 145 in the rear, that is 142f and 145r combo. Or use the dyno jets start small and like you say use the 4th notch, nut much happens with 3rd notch so go up in sizes untill you don't notice anymore torque or better speed on the top end. Keep going up in sizes untill you don't experience any more benefit and stop there and play around with For instance different air mixtures and different heat numbers on spark plugs till you get a lite straw color to the electrode. I have found that no matter how you put your jets in whether small front or small to the back the larger the jet the more torque you will get. The Needle is for mid range and top end as the needle is a gradual slope the mid range will be more gradual and top less noticeable.
Dyno jets will at least seem to run smoother but don't have the torque that the Kawi jets will give you. Your exhaust and intake can only handle so much fuel and the rest is a waste so start small and work to a large enough system that works. Our CDI box is not the best for power as just as the power starts to come on the timing retards and 80% of all power is lost. I have found at least on my dyno at 5000rpm the timing retards by 10 degrees then by 6000rpm it reduces further by another 2degrees for a total of 12 degrees. On some bikes it can retard by as much as 18 degrees. Every vehicle I have worked on the timing always advances as the motor increases in rpm. My son recently baught a crotch rocket a 600cc Suzuki 4cylinder street machine. This thing puts out a whopping 115hp at 14,000rpm. I put it on the dyno and at 6th gear the timing advanced almost 40 degrees and our bikes are actually retarding thanks to the CDI Box. What I am trying to say is no matter what you do for jets and other mods your top will not improve greatly period. If you gain 10% feel lucky because thats all you are going to get unless you are willing to put in another cam. Then you can exspect probably another 10 mph on the top end but that's it only because the CDI box won't allow anything more. I hope this helps if I have forgotten anything let me now.

 

Alltoys
That is basically our exact findings using a dynojet dyno, no two Prairies are exactly the same but the timing is very retarded. We recently got our hands on a pre production factory ignition box[don't ask how] and the timing was not originally retarded as the rpm increase, just one way Kawasakis slowed this beast down. Our black box when finished will put a BIG grin on everyones face.
Bearman